Subject: [Sigtran] M3UA-v02 Last Call Comment: DPC repeated in RK

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Fri, 7 May 2004 19:00:40 -0600

It is unclear whether the DPC parameter is repeated within the RK or whether
the RK is repeated with different DPCs.  It is unclear whether one or both
forms are acceptable.  The offending passage is:

|3.6.1 Registration Request (REG REQ)
|
|   ...
|
|   Destination Point Code:
|
|         The Destination Point Code parameter is mandatory, and
|         Identifies the Destination Point Code of incoming SS7 traffic
|         for which the ASP is registering.  For an alias point code
|         configuration, the DPC parameter would be repeated for each
|         point code.  The format is the same as described for the
|         Affected Destination parameter in the DUNA message (See Section
|         3.4.1).  Its format is:
|
|       0                   1                   2                   3
|       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      |         Tag = 0x020b          |         Length = 8            |
|      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      |    Mask = 0   |            Destination Point Code             |
|      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

I think the intention was that the DPC be repeated within the RK.  If
the DPC can be repeated within the RK, it would be better to repeat the DPC
field within the DPC parameter rather than repeat the parameter (less TL
overhead).  If the DPC can be repeated within the RK or the DPC parameter,
there is no reason not to permit the Mask value to be something other than 0
to indicate a range of DPCs.  With ANSI cluster routing, allowing a Mask value
other than zero would permit an ANSI cluster to be specified.  To establish
routing on Network Appearance as was discussed heavily in the development of
the RFC, there is no reason that the DPC parameter needs to be mandatory.
An absent DPC would imply all DPCs within the NA.  This would avoid sending
DPC with Mask = 0xFF.

Note also that the Affected Destination parameter in the DUNA message can
contain more than one Point Code and does not have a zero Mask value.

Therefore, the format of the Destination Point Code parameter should be:

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x020b          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Mask      |              Destination PC 1                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      \                                                               \
      /                              ...                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Mask      |              Destination PC n                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where the Mask value is as interpreted in Section 3.4.1.

The DPC should be optional instead of mandatory and the absence of the
parameter should indicate all DPCs within the specified or implied Network
Appearance.

--brian

-- 
Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
[email-masked]    ¦ world; the unreasonable one persists in  ¦
http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
                        ¦ Therefore  all  progress  depends on the ¦
                        ¦ unreasonable man. -- George Bernard Shaw ¦

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